The Ebola outbreak continues to roil West Africa, with the World Health Organization announcing Thursday that the death toll has climbed to 729 in Guinea, Sierra Leone and Liberia. More than 1,300 people are infected.

To help limit the spread of the disease the U.S. Centers for Disease Control and Prevention announced the agency is now “surging” its response. Thursday afternoon the agency issued a new level 3 travel warning for the affected countries—asking Americans to halt nonessential travel to those locations and unveiling plans to send 50 additional CDC staff to the affected areas. Once there, CDC workers will help to ramp up airport screenings to ensure that sick people do not leave the country, augment laboratory testing for Ebola and help local health personnel to track individuals who may have been exposed to sick persons. (There is little risk of transmitting Ebola before a person becomes symptomatic, and even then transmission occurs through exposure to bodily liquids, not via the air or water). “The bottom line is that Ebola is worsening in western Africa,” CDC director Tom Frieden told reporters on Thursday. When it comes to controlling this outbreak, “It’s not going to be quick. It’s not going to be easy, but we know what to do,” he says.

Yet containing this outbreak remains a complex undertaking that requires following every potentially exposed individual and isolating them if they become symptomatic—a significant challenge in any location but more so when there are limited health personnel and health infrastructure systems in place. Even in a best-case scenario, Frieden says, this outbreak will not be contained for “three to six months or more.” The international Ebola response is not limited to U.S. aid: Tomorrow WHO is rolling out a new $100-million assistance plan to help tamp down the outbreak.

Despite breathless speculation on the part of many in the media, the risk continues to be largely limited to those African countries instead of the U.S. or Europe. Frieden reiterated that if the highly lethal virus made its way to the U.S., strong health systems—including standard isolation units in hospitals and well-trained health personnel that can trace and track potentially exposed individuals—would help contain the disease. Although CDC personnel (some of whom are doctors) are on the ground in the affected countries, they are focusing on building up the response to Ebola and are not treating patients themselves—leaving such direct care to organizations such as Doctors without Borders.

Right now, without any vaccine or treatment specific to Ebola, the only care hospitals can provide is rehydration and painkillers—although one U.S. aid worker reportedly received blood serum from a teenager who had survived Ebola in the hopes of bolstering the patient's own immune response. Frieden declined to comment on that possibility as a mode of treatment for patients, noting that he has not seen the information and that there are many things we still do not know about recovery from Ebola.